Laser system

ABSTRACT

A laser system having members disposed for rotation and translation and having an X-axis carriage and a Y-axis arm translated on a fixed linear screw and a Z-axis rotation unit including mirrors and pneumatic table providing the capability for three-sided machining of a vehicle chassis.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation in part of U.S. patent applicationSer. No. 07/346,620, filed May 2, 1989, entitled LASER SYSTEM.

FIELD OF THE INVENTION

The present invention relates to laser systems generally and to roboticlaser systems in particular.

BACKGROUND OF THE INVENTION

Various robotic laser systems have been developed and have been utilizedin various applications, such as in automotive production systems. Theserobotic laser systems typically combine a laser system with an existentor an improved robot system, thus reducing development costs.

UK Pat. No. 2,134,071 describes a rotating and translating optical jointcomprising a mirror for directing a collimated laser beam through arobot. An apparatus for moving the joint is also disclosed, as is arobot built from a plurality of such joints.

A combination of two of the joints described in UK Pat. No. 2,134,071which rotate with respect to each other is known as a rotary elbow andis typically placed at every rotary joint of the robot. It is known inthe art that the two mirrors of such a rotary elbow must be maintainedvery accurately parallel in three dimensions. Any misalignment has apotential for causing large deviations of the laser beam. If amisaligned rotary elbow is located roughly 2.5 meters from the end ofthe optical path, a laser beam impinging upon it will be deflected by asmuch as a few millimeters. This deflection reduces the accuracy withwhich the laser beam can be aimed.

There is known a COBRA robotic laser which is built by Ferranti LaserSystems of the UK and which comprises a Ferranti Laser System lasersystem and an ASEA articular robot. The laser beam of the Cobra is splitbefore entering the robot and the two resultant beams are directed alongthe two sides of the ASEA robot. Two rotary elbows, one on each side ofthe robot, are placed at each of the six joints and thus, the systemcomprises 24 mirrors, the entirety of which must be accurately alignedin three dimensions in order to avoid unacceptable divergence of thelaser beam.

U.S. Pat. No. 4,698,483 discloses another robotic laser system, acombination of the "SMART" Robot by Comau of Italy with a laser system.This five degree of freedom system utilizes nine mirrors to bring thelaser beam to the cutting location. Although the number of mirrorsutilized is reduced over the prior art, inaccuracies as described above,resulting from the difficulties involved in aligning nine mirrors,remain.

Yet another robotic laser system, the L-100 manufactured by GeneralMotors Fanuc (GMF) of the U.S., is known in the art. Similar to theother companies described hereinabove, GMF incorporates a laser systeminto an existing robot, however, the robot chosen has simple mechanicsand requires only four mirrors. The robotic system is designed such thatthe laser beam enters the robot vertically from above and impinges upona rotary elbow early in the optical path. If it is desired to combinetwo robots, it is known in the art to add a beam director, whichtypically comprises two mirrors each pointing towards one of the tworobots and which directs the beam horizontally, and one mirror per robotto direct the beam to enter the robot vertically.

The reduced number of mirrors on the L-100 enhances its ability toproduce a laser beam with little divergence and with fairly smalldeviations; however, the existing robot is not designed for theaccuracies required by the optical path. The robot has productiontolerances on its mechanical parts that, as they accumulate, become toohigh to ensure an accurate optical path. Moreover, the rotary elbow atthe beginning of the optical path can cause divergence of the laserbeam.

SUMMARY OF THE INVENTION

There is provided in accordance with a preferred embodiment of thepresent invention a laser system comprising laser apparatus whichprovides a laser beam along a fixed first axis, apparatus forredirecting the laser beam to impinge on a workpiece at a desiredlocation thereon and including apparatus disposed for rotation andtranslation about the fixed first axis which redirects the laser beamalong a second axis and a laser head apparatus arranged to receive thelaser beam along the second axis and to cause it to impinge on theworkpiece at the desired location.

Additionally, according to a preferred embodiment of the invention, theapparatus disposed for rotation and translation comprises a single flatmirror.

Further, according to a preferred embodiment of the invention, the laserapparatus comprises apparatus for receiving the laser beam along a thirdaxis and for redirecting it along the fixed first axis. The apparatusfor receiving the laser beam comprises a beam director which directs thelaser beam in a selectable one of two directions.

Additionally, according to a preferred embodiment of the invention, thelaser head apparatus comprises a cutting head including two flat mirrorsand a concentrating lens. Alternatively, the laser head apparatuscomprises a welding head including a flat mirror and a concentratingmirror. The laser head apparatus rotates about two generally orthogonalaxes.

Further, in accordance with a preferred embodiment of the presentinvention, the optical path length of the laser beam along the fixedfirst axis can greatly exceed the path length from the fixed first axisto the desired location. In addition, the optical path length from thelaser apparatus to the laser head apparatus is considerably longer thanthe optical path length from the laser head means to the desiredlocation.

There is provided according to a preferred embodiment of the invention,a laser system in which the apparatus disposed for rotation andtranslation comprises an x axis carriage, a y axis arm and a z axisrotation unit. According to a preferred embodiment of the invention andin order to provide a relatively rigid structure, the x axis carriageand the y axis arm each translate on a fixed linear screw. The z axisrotation unit comprises a linear screw displaced from a center of the zaxis rotation thereby producing rotation. The linear motion additionallyprovides the system of the present invention with the ability to work onthree of the four sides of a vehicle chassis; conventional articulatedrobots can typically only work on one side of a vehicle chassis.

In accordance with a preferred embodiment of the invention, there isprovided a fixed x axis track along which the x axis carriagetranslates. In accordance with an alternative embodiment of theinvention, the x axis track rotates about the x axis.

Additionally, in accordance with a preferred embodiment of theinvention, the apparatus for redirecting comprises first and secondseparate apparatus for redirecting and wherein the laser apparatuscomprises a single laser. Each separate apparatus for redirectingcomprises three mirrors and the laser apparatus comprises one beamdirector.

In accordance with an alternative embodiment of the invention, theapparatus for redirecting comprises first, second, third and fourthseparate apparati for redirecting and the laser apparatus comprises asingle laser. In this alternative embodiment, the first and secondseparate means for redirecting are located above the third and fourthmeans for redirecting. Each separate apparatus for redirecting comprisesthree mirrors and the laser apparatus comprises three beam directors.

It is, additionally, a feature of the present invention that a minimalnumber of mirrors need be calibrated. For each separate apparatus forredirecting, the mirrors of the laser head apparatus are calibrated withrespect to each other. The remaining mirror, the mirror of the apparatusfor redirecting, is the only mirror inside the laser system which needscalibration. If the laser system includes a beam director, the mirrorsof the beam director are calibrated before calibration of the mirror ofthe apparatus for redirecting.

Enhanced optical path accuracy can be realized by the provision of afixed x axis track. Such a construction enables provision of arelatively long x axis track, having multiple, laser time shared weldingor cutting units mounted thereon.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated more fully fromthe following detailed description taken in conjunction with thedrawings in which:

FIG. 1A is an overall system drawing illustrating the laser weldingsystem constructed and operative according to the preferred embodimentof the present invention;

FIG. 1B is an enlarged illustration showing an x axis carriage useful inthe system of FIG. 1A;

FIG. 1C is an enlarged illustration of a welding head useful in thesystem of FIG. 1A;

FIG. 2 is a pictorial illustration of the generally straight opticalpath of the laser beam of the system of FIG. 1;

FIG. 3A is a pictorial illustration of the optical path of a weldinglaser beam in the welding head of the system of FIG. 1A;

FIG. 3B is a pictorial illustration of the optical path of a cuttinglaser beam in the cutting head of the system of FIG. 1A;

FIG. 4 is a pictorial illustration of the multiplicity of weldinglocations reachable by the system of FIG. 1A;

FIG. 5 is a pictorial illustration of the range of the system of FIG. 1Ain the vertical axis;

FIGS. 6A-6C are pictorial illustrations of possible configurations ofthe system of FIG. 1A;

FIG. 7A is an illustration of a beam director useful in the system ofFIG. 1A;

FIG. 7B is an illustration of a beam director useful in the system ofFIG. 6B;

FIG. 8 is an illustration of an x axis carriage useful in the system ofFIG. 1A;

FIGS. 9A-9D are illustrations of a z axis rotation assembly useful inthe system of FIG. 1A;

FIG. 10 is an illustration of a mechanism to rotate a welding head,useful in the system of FIG. 1A;

FIGS. 11A, 11B and 11C are respective front, side and top viewillustrations of a laser welding or cutting system constructed andoperative in accordance with an alternative embodiment of the presentinvention;

FIGS. 12A and 12B are respective front and top view illustrations of alaser welding or cutting system constructed and operative in accordancewith an alternative embodiment of the present invention; and

FIGS. 13A and 13B are illustrations of part of the optical beam path inthe system of FIGS. 12A and 12B including beam switching apparatusarranged respectively for operation of the first and second cuttingheads formed therein.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Reference is now made to FIGS. 1A-1C which illustrate a laser cutting orwelding system 10 constructed and operative according to the preferredembodiment of the present invention and operating on a workpiece,typically a vehicle chassis 11. The following discussion will describethe system in the context of a laser welding system, it being understoodthat the system is generally utilizable in both applications.

The laser welding system 10 as shown in FIG. 1A comprises a laser head12, such as the MFKP by Ferranti Laser Systems, which produces a laserbeam, and two beam locating assemblies 14 which bring the beam to twoseparate welding locations. Each beam locating assembly 14, in turn,comprises an x axis carriage 16 (FIG. 1B), a y axis arm 18 attached tothe x axis carriage via a y axis frame 19 (FIG. 1B), a z axis bearingunit 20 and a middle bearing unit 22 located at the joining location ofthe two beam assemblies 14, and a welding head 24 for delivering thelaser beam to the welding location. The middle bearing unit 22 typicallycomprises the elements of two z axis bearing units 20. On the weldinghead 24 preferably is a proximity sensor 25 (FIG. 1C) to ensure that thehead 24 comes within a predetermined distance, typically 1-3 mm, ofchassis 11.

A bellows unit 17, attached to two sides of the y axis frame 19, ensuresthat the assembly 14 is completely enclosed. The bellows 17 typicallyensure that dust, other particles, or human hands cannot enter theassembly 14 during its operation and thus, ensures the safety andcleanliness of the system 10.

The directing of the laser beam by one of the beam locating assemblies14 is achieved through movement of units 16-24 as follows. The x axiscarriage 16 translates the y axis arm 18 and the head 24 along a fixed xaxis; the motion is marked by arrow 30. The beam locating assembly 14rotates about the fixed x axis, within a range of ±30° above and belowthe x-y plane as marked by arrow 34. The rotation of the assembly 14 isperformed by z axis unit 20 and middle bearing unit 22 and producesmotion generally in the z direction. The y axis arm 18 translates thehead 24 along the y direction, as marked by arrow 32. The head 24 hastwo axes of rotation as shown in FIG. 1C; an azimuthal axis 35 parallelto the y axis and an elevation axis 37 perpendicular to azimuthal axis35. The rotations are indicated by arrows 36 and 38, respectively. Itwill be appreciated that the x axis is the only fixed axis of thesystem; the locations of the remaining axes are variable and dependgenerally on the location of the x axis carriage 16.

Each laser system 10 described hereinabove is typically about 3 m long,2 m wide and 2 m high and typically stands 1.5-2.5 m from the chassis11. The y axis arm 18 typically maximally extends 1.6 m and the z axisrotation typically produces a range of about 2 m. The entirety of twosystems 10 is typically about 7 m; in comparison, a chassis 11 istypically 3.5 m.

Reference is now made to FIG. 2 which indicates the generally straightoptical path which the laser beam, denoted 40, follows. It will beunderstood that a "straight" optical path is one in which there are norotary elbows. Any changes in direction of the laser beam are performedby single mirrors.

The laser head 12 produces beam 40 and directs it in a typicallyvertically downward direction. The beam 40 passes through an externalconduit 42, impinges upon one of two flat non-rotating mirrors 43, suchas copper gold coated mirrors manufactured by SPECAC of the UK, of abeam director 44, and is subsequently redirected, in its entirety, alongthe x axis of one of the beam assemblies 14. It should be noted that thelength of the external conduit 42 is the extent of the external beamdelivery. It should also be noted that at any given time, only onesystem 10 receives the laser beam 40.

The internal beam delivery is performed as follows. The beam 40 leavesthe beam director 44 and subsequently impinges upon a flat mirror 46,such as a gold coated copper mirror, located in a fixed location on xaxis carriage 16. The length of the x axis beam delivery is variable anddepends upon the location of the x axis carriage. Bellows 17 shrink andexpand in accordance with the motion of the x axis carriage 16 andtypically ensure that the laser beam 40 is completely enclosed.

From its location on the x axis carriage 16, mirror 46 directs the beam40 along the y axis arm 18 and inside a bellows 48 a flat mirror 50,such as a gold coated copper mirror by Specac, located in the head 24.The length of the y direction delivery is variable and depends on theextension of the y axis arm 16; it is typically shorter than the x axisbeam delivery length. Additionally, as can be seen from the descriptionhereinabove, the external beam delivery is typically short with respectto the internal beam delivery.

Mirror 50 bends the beam 40 towards a concentrating mirror 52, such as acopper covered molybdenum parabolic mirror by Specac, which subsequentlyconcentrates the beam 40 and directs it towards the desired weldinglocation on chassis 11. FIG. 3A shows the welding head 24 and theoptical path through it in more detail.

According to an alternative embodiment of the present invention, thewelding head 24 is a cutting head 51, as shown in FIG. 3B. According tothis second embodiment, mirror 52 is a flat mirror, such as a goldcoated copper mirror by Specac, which directs the beam 40 to a lens 53,such as a ZnSe lens with double anty reflective coating by Specac,which, in turn, directs the beam 40 to the cutting location.

According to both embodiments, mirrors 50 and 52 of welding head 24constitute a rotary elbow and rotate about axes 35 and 37, respectively;these rotations are the only rotations in an otherwise generallystraight optical path, and they occur at the end of the path. It shouldbe noted that the length of the optical path through the welding head 24to the welding location on chassis 11 is considerably shorter than thelength of the optical path up to the welding head 24. Thus, anymisalignment between the two mirrors 50 and 52 of the welding headcauses minimal divergence of the beam 40 at the welding location.

It should be noted that the welding head 24 can be any suitable weldinghead and the cutting head 51 can be any suitable cutting head; theconditions of their operation are outlined hereinabove along with apreferred embodiment.

Three features of the present invention are that the x axis is fixed inspace, that it is both an axis of translation and an axis of rotationand that the beam 40 is directed along it. Thus, it is additionally afeature of the present invention that mirror 46 operates to direct thebeam 40 along three axes, the x, y and z axes. The location of mirror 46on the x axis, which changes as the x axis carriage 16 translates,defines the length of the x axis beam delivery. From its current x axislocation, mirror 46 directs the beam 40 in the y direction. Finally, asassembly 14 rotates about the x axis, mirror 46 also rotates and in thismanner, directs the beam 40 in the z direction.

The utilization of mirror 46 for direction of the beam 40 in three axesresults in a significant reduction in the number of mirrors over theprior art and a corresponding reduction in the time necessary forcalibration of the system. An additional improvement is that translationalong the x axis and rotation about it does not affect the accuracy ofthe x axis beam delivery.

The requirement of a generally straight optical path has mechanicaladvantages, such as a relatively rigid mechanism and ease in approachinga multiplicity of welding locations on the chassis 11. FIG. 4illustrates four welding locations typically reached by a pair of laserwelding systems 10a and 10b where each system 10 has two positions.Position 1 is denoted with solid lines and position 2 is denoted withdashed lines. Welding head 24a of system 10a operates on the left backcorner of chassis 11 at generally the same time that head 24b operateson the center of the right side panel. Alternatively, as shown inposition 2, head 24a can operate on the center of the right side panelwhile head 24b operates on the front panel of chassis 11. FIG. 4additionally shows that there is an overlap region in the center of thechassis 11 within which both systems can operate. It will be appreciatedthat other combinations of two welding locations, other than those shownin FIG. 4, is possible.

Reference is now made to FIG. 5 which illustrates the range of movementof two systems 10 in the vertical or z direction. Head 24a is shownwelding underneath chassis 11 at generally the same time that head 24bis welding on the roof of chassis 11. As can be seen from FIG. 5, head24b typically does not reach the entirety of locations on the roof ofchassis 11. This problem is solved, in an alternative embodiment, byraising the height of base supports 60 and is shown in more detail inFIG. 6A.

FIG. 6A illustrates a pair of welding systems 10 whose base supports 60have been raised by a height large enough to ensure that the y axis arm18 can reach over the top of chassis 11. The higher location shown inFIG. 6A is useful for reaching locations on the roof of the chassis 11.As was shown with respect to FIG. 4, the y axis arm 18 reaches to thefar side of the chassis 11.

In the alternative embodiment shown in FIG. 6A, the laser system 12 islocated below the systems 10 and thus, the laser beam 40 is firstdelivered in a vertically up direction. In all other respects, theconfiguration of FIG. 6A operates as described hereinabove. FIG. 6A alsoillustrates an alternative configuration of the laser system 12, that ofparallel to the systems 10 rather than perpendicular to it as has beenshown hereinabove.

It will be appreciated that the laser system of the present invention ismodular. Two systems 10 can be placed at different heights relative tothe chassis 11, as has been described hereinabove, or they can beconfigured as a unit of four systems 10 consisting of a first twosystems at one height and a second two systems above the first twosystems, as described hereinbelow with respect to FIG. 6B.Alternatively, a welding station of eight systems, four on each side, ispossible. Further, as described hereinbelow with respect to FIG. 6C, onesystem 10, generally the length of chassis 11, can be used in place oftwo systems 10 as has been shown hereinabove.

FIG. 6B illustrates the configuration of four welding systems. Thisalternative embodiment enables four locations of the chassis 11 to bewelded at generally the same time. The laser beam 40 is delivered fromthe laser system 12 to a beam director 44a which directs the beam 40either vertically downward to the beam director 44b of the lower twosystems 10 or vertically upward to the beam director 44c of the uppertwo systems 10. The beam director 44b or 44c which receives the beam 40then redirects it to the system 10 which is to perform the welding atthe current time. It will be appreciated that the beam director 44a willface sideways, that beam director 44b will face upward and that the beamdirector 44c will face downward, as will be described in more detailhereinbelow.

FIG. 6C illustrates an embodiment of one system 10 generally the lengthof chassis 11. In this embodiment, the laser system 12 delivers the beamhorizontally along the fixed x axis of the system eliminating the needfor a beam director 44. Accordingly, this embodiment has only threemirrors, 46, 50 and 52.

Reference is now made to FIG. 7A which illustrates the mechanism of anupwardly facing beam director 44. Beam director 44 is typically locatedon the lower face of middle bearing unit 22 and comprises two directingmirrors 43a and 43b for directing the laser beam 40 to the laser weldingsystem 10 on the left of the beam director and to the system 10 on theright of the beam director, respectively. The mirrors 43 are typicallyattached to a precision pneumatic table 74, such as the HO 2075manufactured by THK of Japan, which operates to precisely locate one ofmirrors 43 to receive beam 40 and to redirect it along the x axis of theappropriate one of a pair of systems 10. Pneumatic table 74 typicallytranslates along the y axis of the system as shown by arrow 75.

Each mirror is set at a precise 45° angle to the entrance axis of thebeam 40; as shown in FIG. 7, mirror 43a faces to the left and mirror 43bfaces to the right.

In an alternate embodiment of the beam director, as described withrespect to FIG. 6B, a downwardly facing beam director 44 is located onan upper face of the middle bearing unit 22. In a third embodiment ofthe beam director, shown in FIG. 7B and as described with respect toFIG. 6B, the beam director 44a is located on the side wall of the middlebearing unit 22. The mirrors 43 direct the beam 40 vertically upward orvertically downward and the pneumatic table 74 translates along the xaxis. In the other two embodiments, the downwardly and upwardly facingbeam directors, the pneumatic table 74 translates in the y direction.The other details of the beam director 44 remain the same for both ofthe abovementioned embodiments.

Reference is now made to FIG. 8 which illustrates the generally rigidtranslational mechanism in the x axis and y direction and itscoordination with the generally straight optical path. The mechanismcomprises a DC servo motor 80, such as the JR16M4CHF12T manufactured byPMI of the U.S., located on the x axis carriage 16, which rotates a nut82 via a timing belt 84 and causes the x axis carriage 16 to translatealong a fixed leading ball screw 86, such as the 1512-4-9004manufactured by Star of W. Germany. The y axis arm 18 is typicallytranslated through the y axis frame 19 in a similar manner, typically bya servo motor 88, such as the JR24M4CHF12T by PMI, a timing belt 90, anut 92 and a fixed ball screw 94 similar to ball screw 86. It will beappreciated that the use of fixed ball screws 86 and 94 ensures agenerally rigid ans accurate movement and additionally provides agenerally smooth motion.

FIG. 8 also indicates the coordination of the optical path with thetranslating mechanism. As mentioned hereinabove, it is a feature of theinvention that beam 40 is directed by one of the mirrors 43 of beamdirector 44 along the fixed x axis of the system 10. Thus, in order toensure that nothing interferes with the optical path, the fixed leadingball screw 86 is located along an axis parallel, but not equivalent tothe fixed x axis.

Mirror 46 is typically located on the x axis carriage 16 on the sideclosest to the beam director 44 and in front of the y axis arm 18 andthe screw 94. The optical path in the y direction, covered by bellows48, is thus separate from the translation mechanism. In the system ofFIG. 6C, mirror 46 is located on the x axis carriage 16 on the sideclosest to the location of the laser head 12.

As mentioned hereinabove, the fixed x axis, as defined by the path ofthe light beam 40, is the axis of rotation of the beam locating assembly14. The mechanism which performs the rotation of the assembly 14 aboutthe fixed x axis utilizes a linear screw at a predetermined distancefrom the center of rotation thereby to ensure a relatively smooth andaccurate motion, as shown in FIGS. 9A-9D and as is described in detailhereinbelow.

With reference to FIGS. 9A and 9B, beam locating assembly 14 iscomprised of two large rings 102a and 102b and a frame 103 which istypically integrally connected to them and to which is attached theentirety of the mechanism of the x axis carriage 16. The large rings102a and 102b are located in the middle bearing unit 22 and in the zaxis unit 20, respectively, and rotate on two thin section, widediameter bearings 100, such as the RB60040UU by THK. An extension 104 istypically attached to frame 103 near large ring 102a. A rotatingassembly 106 (FIG. 9B), generally connected to the base support 60 ofmiddle bearing unit 22 but standing outside of it, rotates extension 104causing frame 103 to rotate on bearings 100 and producing the z axismotion of assembly 14.

Rotating assembly 106 comprises a DC servo motor 110 (FIG. 9B), such asthe JR24M4CHF12T by PMI, which rotates a timing belt 112, whichsubsequently rotates a ball screw 114, such as the 1512-5-4004 by Star,through a bearing 115. Ball screw 114 rotates inside a nut 116 which isattached, via pin 118, to extension 104. As ball screw 114 rotates,extension 104, and thus, assembly 14, rotates. To accommodate theresultant change in angle between the extension 104 and the ball screw114, the nut 116 is attached to pin 118 and thus, can oscillate.Additionally, the motor 110 and the ball screw 114 are attached to aflange 120 which oscillates on a axle 122 typically connected to base 60of bearing unit 22.

FIG. 9B shows the rotating assembly 106 with the extension 104 in acentral position, and FIGS. 9C and 9D show the rotating assembly withthe extension 104 at two opposite and generally extreme positions. Itwill be appreciated that the combination of a ball screw produced linearmotion about very large bearings produces a generally rigid z directionmotion.

Reference is now made to FIG. 10 which illustrates a mechanism forrotating the elements of welding head 24. A DC servo motor 130, such asthe HDSA-20 by Harmonic Drive of Japan, attached to y axis arm 18,rotates the welding head 24 about axis 35 via a timing belt 132 and agear 134. This movement causes mirror 50 to rotate.

A DC servo motor 136, similar to motor 130 and attached to welding head24, rotates mirror 52 and a nozzle 138, via a timing belt 140 and a gear142. It will be appreciated that the two axes of rotation provided bythe welding head 24 ensures that the nozzle 138 typically directs thebeam 40 at the chassis 11 at an angle generally perpendicular to thewelding location of chassis 11.

Reference is now made to FIGS. 11A-11C, which illustrate an alternativeembodiment of the present invention, which is essentially similar to thesystem described hereinabove, except that here a fixed x axis track 150is provided. Mounted for accurate translation along track 150, as by aball screw 152 is an X-axis carriage 154.

A laser beam directing unit 156 is arranged for precise angular rotationabout a Z axis, typically parallel to the X axis, driven as by anelectric motor driven screw drive assembly 158. Unit 156 typicallyincludes a base portion 160 onto which is mounted an extensible arm 162,which extends along a Y axis and has mounted at an extreme outer endthereof a cutting head 164, which may be any suitable laser cuttinghead, or alternatively a welding head, such as those describedhereinabove.

The essential features of the optical path of the apparatus describedabove in connection with FIGS. 1-10 are also present in this embodiment.Here a laser beam from a laser head 166 is reflected by a stationarymirror 168, which may be rigidly mounted onto track 150, to extend alongthe Z axis, which is effectively both the axis of translation and ofrotation.

It is a particular feature of the embodiment of FIGS. 11A-11C, that theprovision of a stationary X axis track enables a very long track to beprovided, since it is not necessary to rotate the track as in theearlier described embodiments. This advantage may be appeciated by aconsideration of FIGS. 12A and 12B, which illustrate an embodiment ofthe invention, similar to that of FIGS. 11A-11C, but including multiplelaser beam directing units 156, each of which may operate independently,but preferably time shared with a single laser source. It is aparticular feature of the arrangement of FIGS. 12A and 12B, thatsufficient numbers of directing units 156 may be mounted on a singletrack 150, to enable redundant units to be provided, to provide backupin case of breakdown of one or more units. The provision of multipledirecting units 156 also enables significantly higher throughout for agiven floor area to be achieved than through use of prior art systems.

Reference is now made to FIGS. 13A and 13B, which illustrates a laserbeam time sharing optical system which is particularly useful in thesystem of FIGS. 12A and 12B. Switching of the laser beam from a first toa second beam directing unit 156 may be readily achieved, as shown, bythe use of a mirror 170 located in association with a first beamdirecting unit 168, which is arranged for selectable movement in an outof the laser beam path along the Z axis. When the mirror 170 is movedinto the Z axis beam path, as shown in FIG. 13B, it reflects the laserbeam into operative association with the first beam directing unit 168,along its Y axis.

When the mirror 170 is moved out of the Z axis beam path, as illustratedin FIG. 13A, the laser beam impinges only on the mirror forming part ofthe second beam directing unit 156. It is appreciated that multiple beamdirecting mirrors 170 may be associated respectively with multiple beamdirecting units 156, so as to enable laser beam switching among morethan two beam directing units 156 in essentially the same manner asillustrated and explained hereinabove. The mirrors 170 may be mountedfor relatively quick movement into and out of the Z axis laser beam pathso as to permit a relatively large number of beam directing units 156 tobe employed simultaneously, without reducing their time efficiency dueto time sharing of the laser beam.

It will be appreciated by persons skilled in the art that the presentinvention is not limited by what has been particularly shown anddescribed hereinabove. The scope of the present invention is definedonly by the claims which follow.

I claim:
 1. A laser system comprising:laser means providing a laser beamalong a fixed generally horizontal first axis; means for redirectingsaid laser beam to impinge on a workpiece at a desired location thereonand including; means disposed for rotation about and translation alongsaid fixed generally horizontal first axis for redirecting said laserbeam along a second axis, said means rotating on a non-rotatable base;laser head means arranged to receive said laser beam along said secondaxis and to cause it to impinge on said workpiece at said desiredlocation.
 2. A laser system according to claim 1 and wherein said meansdisposed for rotation and translation comprises a single flat mirror. 3.A laser system according to claim 1 and wherein said laser meanscomprises means for receiving said laser beam along a third axis and forredirecting it along said fixed first axis.
 4. A laser system accordingto claim 3 and wherein said means for receiving said laser beamcomprises a beam director which directs said laser beam in a selectableone of two directions.
 5. A laser system according to claim 1 andwherein said laser head means comprises a cutting head including twoflat mirrors and a concentrating lens.
 6. A laser system according toclaim 1 and wherein said laser head means comprises a welding headincluding a flat mirror and a concentrating mirror.
 7. A laser systemaccording to claim 5 and wherein said laser head means includes twomirror elements which rotate about two generally orthogonal axes.
 8. Alaser system according to claim 6 and wherein said laser head meansincludes two mirror elements which rotate about two generally orthogonalaxes.
 9. A laser system according to claim 1 and wherein the opticalpath length along said fixed first axis can greatly exceed the length ofthe optical path from said fixed first axis to said desired location.10. A laser system according to claim 1 and wherein said optical pathlength from said laser means to said laser head means is considerablylonger than the optical path length from said laser head means to saiddesired location.
 11. A laser system according to claim 1 and whereinsaid means disposed for rotation and translation comprise an x axiscarriage, a y axis arm and a z axis rotation unit.
 12. A laser systemaccording to claim 11 and wherein said x axis carriage translates on afixed linear screw thereby to produce a smooth and rigid motion.
 13. Alaser system according to claim 11 and wherein said y axis armtranslates on a fixed linear screw thereby to produce a smooth and rigidmotion.
 14. A laser system according to claim 11 and wherein said z axisrotation unit comprises a linear screw displaced from a center of the zaxis rotation thereby to produce a smooth and rigid rotation.
 15. Alaser system according to claim 1 wherein said means for redirectingcomprises first and second separate means for redirecting and whereinsaid laser means comprises a single laser.
 16. A laser system accordingto claim 1 wherein said means for redirecting comprises first, second,third and fourth separate means for redirecting, wherein said lasermeans comprises a single laser and wherein said first and secondseparate means for redirecting are located above said third and fourthmeans for redirecting.
 17. A laser system according to claim 15 andwherein each separate means for redirecting comprises three mirrors andwherein said laser means comprises a single beam director.
 18. A lasersystem according to claim 16 and wherein each separate means forredirection comprises three mirrors and wherein said laser meanscomprises three beam directors.
 19. A laser system according to claim 1and wherein said non-rotatable base comprises a fixed elongate track andwherein said means arranged for rotation and translation also compriseat least one carriage movable along said elongate track parallel to saidfixed first axis.
 20. A laser system according to claim 19 and whereinsaid at least one carriage comprises a plurality of carriages and saidmeans arranged for rotation and translation includes means for timesharing of said laser beam among a plurality of laser head means, eachassociated with one of said plurality of carriages.